Rare earth magnet and method therefor

Abstract

A rare earth magnet includes rare earth magnet particles; and amorphous and / or crystalline terbium oxide present at the boundary of the rare earth magnet particles and represented by the formula: TbOn, wherein 1.5<n≦2. The rare earth magnet prevents decrease eddy current effectively.

Description

Background of the Invention [0001] 1. Field of the Invention [0002] The present invention relates to a rare earth magnet having high electric resistance, and in particular, relates to a rare earth magnet with high electric resistance to be used in a motor for electronic equipment and automobile driving. [0003] 2. Description of Related Art [0004] An inexpensive ferritemagnet has conventionally been used widely as a magnet for a permanent magnet type motor. However, use of a rare earth magnet with higher performance has been increasing year by year with demand for development of more compact rotating electrical appliances with higher performance. Development of a rare earth magnet, represented by Sm—Co type magnet and Nd—Fe—B type magnet, is under way, aiming at higher performance and lower price. A rare earth magnet, however, has low electric resistance because it is a metal magnet, leading to a problem of lowering a motor efficiency due to increased eddy-current loss when built in ...

AI Technical Summary

Benefits of technology

The patent text describes a rare earth magnet with improved magnetic characteristics and stability. The magnet includes rare earth magnet particles and amorphous or crystalline terbium oxide present at the boundary of the particles. The addition of silicon dioxide and aluminum dioxide to the magnet reduces its electric resistance but lowers its magnetic characteristics. Using a metal oxide of rare earth elements, such as yttrium, can improve the stability of the magnet. However, using a sol containing an alkoxide of rare earth elements can cause problems during production. The rare earth magnet produced by this method has effective suppression of eddy current and minimal degradation of magnetic characteristics.

Problems solved by technology

However, when SiO2 and / or Al2O3 are added alone to the rare earth magnet, magnetic characteristics thereof are significantly lowered, making application of the magnet to a motor with medium to high output difficult.

A metal oxide (MO(n / 2)) of a metal M (Si, Zr, Ti, Al, Cr, Ce and Co) described in JP-A-6-69009 is so poor in thermodynamic stability that chemical reaction proceeds between magnet particles and a metal oxide layer (MO(n / 2)) in a fixing step by heating under compression, resulting in significantly lowered magnetic characteristics of the rare earth magnet.

Consequently, when an amorphous metal oxide layer (MO(n / 2)) is formed at the boundary of magnet particles by a sol-gel method starting from a metal alkoxide of a rare earth element including Y, produced sol is easily gelled, then posing a problem of forming a coated film with rough surface caused by gel particles grown large in a liquid or a problem of forming turbid liquid or deposit caused by gelation of most part of sol.

In other words, stable production of a rare earth magnet is difficult, when sol containing an alkoxide of a rare earth element such as Y is used for producing a rare earth magnet.

As described above, conventional technologies have posed problems of significantly lowering of magnetic characteristics and inability of stable production of a rare earth magnet, although they can suppress eddy current generation by increasing electric resistance of a rare earth-magnet.

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